Laboratory Manual

Objectives:

This document provides an introduction and overview of the lab activities for the EE223 module. Please read this carefully before attending the lab sessions.

There are four "Digital" and two "Analogue" Lab sessions in total. Each session lasts three hours. Completing the lab activities is a required component of the module and be careful, there is no resit opportunity for the laboratories during the summer (the grade that you get in CA in Semester 1 will be the grade that is used for calculation in the resit examination session). These will be graded, and will contribute a total of 30% of your overall mark for the EE223 module.

General Instructions:

Study the instructions for each lab exercise in detail, in advance of each scheduled lab session. If you do not do this, you will almost certainly not be able to complete the assigned exercise in the available time during the session. (In general, your mark for a lab session will be reduced, pro rata, if you do not complete the assigned work.) Note that, in general, this means that you will have to research and develop your knowledge of relevant prior concepts (i.e., to locate and study appropriate "external" resources, such as textbooks etc.); and you should also have completed all the prior weekly worksheets.

You must attend punctually. Attendance will normally be recorded in the first 15 minutes of the session: if you arrive after the attendance is taken, you will be recorded as absent.

If you are recorded as absent from any compulsory attendance lab, you must submit a written explanation, with appropriate documentation (e.g., medical certificate etc.) to Dr. Derek Molloy. If you omit to do this, you will be recorded as having failed the laboratory and will receive a mark of zero for that laboratory.

You will normally work in groups of two students in each session. You should self organise into such groups on arrival (or beforehand, if you prefer).

Ask a demonstrator if you are unsure of anything. In particular, if you have any doubt about the safety of any procedure, you must discuss this with a demonstrator beforehand.

Complete all sections of each lab. Show all recorded data, and answers to questions, clearly in your logbook.

The laboratory Logbook Notes:

Each student must have their own individual laboratory notebook or logbook. A single EE223 logbook will be common to both Digital and Analogue lab sessions for the module.

You must complete the report on each lab after the lab session. You will have to submit a digital write-up of your laboratory through Moodle, so the notes that you take during the lab session will be vital to your final electronic write-up.

If no template is provided for a laboratory write-up, start the report for each lab session on a new page, with a clear heading, e.g.:

Digital Electronics: Lab Session 1

Basic Combinatorial Logic

Date: 27 Oct 2012

Partner Name: Zaphod Beeblebrox

Except where you are explicitly told otherwise, please do not copy any material from the instructions for the particular lab session into your logbook.

Number each section/subsection of your report clearly. (If the instructions for the particular lab session are already numbered, then follow this numbering system in your report also.)

Graphs, diagrams, figures etc. must be labelled with a number and a descriptive title (e.g., "Figure 1: Breadboard Wiring Layout", "Graph 3: Clock Pulse Waveform" etc.). If a graph or figure is referenced in your text this should be done using its assigned number (e.g., "As shown in graph 6, the maximum voltage detected was ..." etc.).

Both axes on a graph must be labelled with the quantity recorded (matching the labels in the corresponding data table, if any) and the specific units of measure (V, s, A, etc.).

You can either plot your graphs electronically, or you can take a photograph of a diagram that you have carefully drawn.

Equipment:

The main equipment used in these labs consists of:

Your personal DCU Electronic Engineering electronics kit. Please make sure to bring one kit along to each lab per group.

Digital integrated circuits (ICs). The appropriate ICs for each session should be in your kit or will be made available by the technical staff. You are responsible for selecting which ones you need for each activity. If you suspect than an IC may be damaged, please make sure to inform the demonstrators or technical staff accordingly.

Meters: you may need to measure specific voltage values. Use an appropriate digital or analogue voltmeter, provided at the lab workstations, for this purpose. Again, if in any doubt about the use of the meters, please check with a demonstrator.

Connecting wires. The kit and the technical staff will provide a selection of pre-cut connecting wires, and also access to spooled wire and wire cutters/strippers. You are responsible for selecting whatever connecting wires you need for each activity. Please adopt some basic colour coding: red and black for power supplies (5V and 0V respectively); other colours for signals, as appropriate.

Breadboards:

Breadboards are used for these laboratories on which you can assemble your experimental circuits. Each breadboard consists of two terminal strips and two bus strips. Each bus strip has two rows of contacts. Each of the two rows of contacts are a node. That is, each contact along a row on a bus strip is connected together (inside the breadboard). Bus strips are used primarily for power supply connections, but are also used for any node requiring a large number of connections. Each terminal strip has 60 rows and 5 columns of contacts on each side of the centre gap. Each row of 5 contacts is a node.

You will build your circuits on the terminal strips by inserting the leads of circuit components into the contact receptacles and making connections with 22-26 gauge wire. There are wire cutter/strippers and a spool of wire in the lab. It is a good practice to wire +5V and 0V power supply connections to separate bus strips on any given breadboard.

The bench equipment can supply a 5V power supply and a pair of +15V to -15V supplies. For the Digital electronics labs we will use only the 5V supply. Please take care to connect the 5V supply with the correct polarity; and not to connect the ±15V supplies to any of the circuits used in these labs: doing so may result in damage, including rapid over-heating, which may be dangerous to the people working on the experiment. Always double check all circuit connections before applying power.

Figure 1 The breadboard. The orange lines indicate connected holes.

Tenma Multimeter:

Throughout the experiments and laboratories we will use a digital multimeter to measure values of voltage, current and resistance. Please see the operating manual for instructions on how to use your digital multimeter. Tenma Multimeter Operating Manual

Building the Circuits:

Throughout these experiments we will use Transistor-Transistor-Logic (TTL) chips to build circuits. The steps for wiring a circuit should be completed in the order described below:

Turn off the power before you build anything!

Make sure the power is off before you build anything! (Have you checked?)

Insert the chips you will be using into a breadboard. Point all the chips in the same direction with pin 1 at the left corner. (Pin 1 is normally identified by a dot or a notch next to it on the chip package).

Connect +5V and GND (0V) pins of each chip to the power and ground bus strips on the breadboard.

Select a connection on your circuit schematic and place a piece of hook-up wire between corresponding pins of the chips on your breadboard. It is better to make the short connections before the longer ones. Mark each connection on your schematic as you go, so as not to try to make the same connection again at a later stage.

You can use switches from your kit, but sometimes simple connections to +5V or GND are fine.

Similarly, to can use LEDS from your kit to conveniently monitor the state of outputs from your circuits.

You should never connect the outputs of two separate gates directly together.

You may connect any given signal to several gate inputs in parallel.

Your final connections for each circuit should be between the power rails on your breadboard(s) and the "hardwired" power rails. Make sure to get the polarity right, and to connect only to the +5V supply. This is much easier if you consistently use colour coding for your wiring (red and black for the +5V and GND power supply lines respectively; other colours for signals, as appropriate).

If one member of the group makes the connections for a particular circuit, then the other should check all the connections, before you turn the power on.

Finally, switch on the power. Watch for any sign of malfunction - e.g., burning, smoke, etc. If you notice such signs, at any time, switch off the power immediately. Check with the demonstrator before doing anything further.

When you switch on the power for the first time in any given lab session, measure the voltage on the +5V supply rail, and verify that it is correct. If in doubt, switch off and check with a demonstrator.

Always switch off the power again before starting to rewire or re-configure the circuit in any way.

At the end of the laboratory session, collect your hook-up wires, ICs etc., and file them away in your kit in the appropriate locations.

Tidy the area that you were working in and leave it in the same condition as it was before you started.

Common Causes of Problems:

In all experiments, you will be expected to obtain all instruments, leads, components at the start of the experiment and return them to their proper place after you have finished the experiment. Please inform the demonstrator or technical staff if you locate faulty equipment. If you damage an IC, inform a demonstrator. Please do not put suspect components back in the box for somebody else to use.

Very common causes of problems in these labs include:

Not connecting the ground and/or power pins for one or more ICs.

Connecting the power with the wrong polarity on one or more ICs.

Not turning on the power supply(!).

Leaving out wires.

Plugging wires into the wrong holes.

Connecting the outputs of two or more gates directly together.

Modifying the circuit while the power is still on.

Example Breadboard Implementation of a Logic Circuit:

Suppose you need to build a circuit to implement the Boolean function F = /(/A./B). Please note that the notation /X is used here to denote logical inversion (complementation, or applying the NOT operator). You should use this notation during the write-up of your laboratory experiments.

7400: Quad 2 Input NAND

7404: Hex Inverter

Fig 2. The complete designed and connected circuit

Place your ICs in the same direction, to save confusion at a later stage. Remember that you must connect power to the chips to get them to work.